Lloris was knocked out in a clash with Everton striker Romelu Lukaku last weekend, and Villas-Boas was widely criticised for allowing his visibly concussed No. 1 to stay on the field.
Andre Villas-Boas: "Clinically and medically all the signs were that the player was ready to play.
"It was down to the ImPACT test -- the medical staff value it a lot. They felt it was too soon and I had to stick to what they said.
"In the incident last week we did everything according to the book.
"We gave the first half advantage to Newcastle, although I think we were very unlucky during all of the game.
"We had so many good chances that I think the result is very unfair.
"Obviously Newcastle came in strong and really played well in the first half.
"I think they deserved to get that lead, I think we didn't recognise ourselves in the first half.
"We were not on top of our game and let ourselves be anticipated a lot. It wasn't one of our better first halves.
"Still we had some good opportunities in the first half, then in the second half if we had been a bit more lucky we could have drawn the game and gone on from there.
"Disappointing because it's not what we deserved. We gave a good response in the second half.
"Last season he had a great game here as well, and today he (Tim Krul) was the inspiration.
"He made the difference today."
Source: Newcastle United Mad